482 
LEPIPOPTERA. 
In the first place we find that in some species the pupa is provided 
with means of forcing itself out, so that the imago can emerge free to 
the open air. Micropteryx is a conspicuous example, in which the 
pupa has a very large pair of mandibles, with which it cuts through 
the cocoon and, having done so and forced its way out with the aid 
of spines on the abdomen, the mandibles are shed. The imago is 
then free to emerge unimpeded by the cocoon. The same occurs in 
Myrmeleo, in Hemerobius and in the Phryganeides ; (this is only one 
of the reasons adduced to support the view that Micropteryx is 
closely related to the Phryganeides). Actually it is the muscles of the 
imago which move the large pupal jaws, but the latter are an essential 
pupal character and absent in the emerged adult. In another group, 
in which pupal emergence occurs, we find that the pupa has hard 
processes on the head and that the body is much ciliated to give it a 
grip on the cell ; an instance is the pupa of the Bombyliid, Anthrax, 
parasitic in the nest of mason bees. In several groups of Lepidoptera, 
the pupa wriggles half way out of the cocoon or shelter and then the 
imago emerges. This is seen in the male of Psychidce (fig. 328) in 
many Sesiidce and Tortricidce (PL LII), and in Cossidce (fig. 330). In 
some of these, there are not only abdominal spines, but on the head a 
strong process used for piercing the cocoon. We may remind the 
student that the bulk of Heterocerous pupse are firmly attached to the 
cocoon by the terminal process and so cannot move out; the families 
mentioned here are in a minority in utilising the activity of the pupa. 
The more general device is some arrangement by which the imago 
can emerge. One of the most striking is the secretion of solvents which 
either dissolve or soften the cocoon, releasing the imago. Latter proved 
the presence in the Puss Moth Cocoon of free Potassium Hydroxide, and 
further states that the imago is itself protected by a part of the pupa 
skin when it pushes through the softened cocoon (Trans. Ent. Soc. 
1895, p. 399). The same principle is utilised by the silk moth ( Bombyx mori) 
and by some Saturniidce. For this reason silk can be reeled only from 
cocoons from which the moth has not emerged, as the solvent is injurious 
to the fibres of the silk. In a number of species of Saturniidce, this process 
is supplemented or replaced by the action of two spines, one on each 
forewing at the base of the costal edge; the imago emerges with crumpled 
wings and with the spines projecting forward before the head; these are 
used to cut through the cocoon and allow the moth to emerge. This occurs 
in the genera Saturnia, Actias and Anthercea. In Attacus this does not 
occur, but the cocoon is spun with one end closed with thread loops, in 
such a way that anything trying to get in, forces the loops together, 
but the moth, emerging from within, forces the loops apart. Similar devi¬ 
ces are far more common probably than are now recorded ; in Earias 
fabia, for instance, the cocoon is of peculiar shape, and the lips of one end 
close mechanically ; the moth pressing from within escapes easily and the 
lips gape readily if the cocoon is pressed from above ; but it resists any 
attempts at entrance from without. It would be of great interest to 
